Burner system with heated spray chamber for spectroscopic analysis



Apnl 15, 1969 A. HELL. 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS FiledJan. 21, 1964 Sheet of z mvrsmon AUGUST HELL ATTORNEY Aprll 15, 1969 A.HELL 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS FiledJan. 21, 1964 Sheet 2 of s INVENTOR AUGUST HELL FIG. 4 B.Y/7 W;(

ATTORNEY Aprll 15, 1969 A. HELL 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS FiledJan. 21, 1964 Sheet 3 of 3 FIG. 5

INVENTOR.

' AUGUST HELL ATTORNEY United States Patent Oflice 3,438,711 PatentedApr. 15, 1969 3,438,711 BURNER SYSTEM WITH HEATED SPRAY CHAM- BER FORSPECTROSCOPIC ANALYSIS August Hell, Whittier, Calif., assignor toBeckman Instruments, Inc., a corporation of California Filed Jan. 21,1964, Ser. No. 339,218 Int. Cl. G01n 21/00; G013 3/00; B05b 1/14 US. Cl.356-36 22 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus forobtaining a larger concentration of atomic vapor greater than thatheretofore obtainable particularly for use in atomic absorptionspectroscopic analysis are disclosed. The method includes the steps ofspraying a sample dissolved in a solvent into a heated chamber where thesolvent is evaporated, delivering the vaporized solvent and the sampleto a condensing chamber for condensing the solvent, mixing the remainingsolvent and sample with a fuel and igniting the result ing mixture.Apparatus is disclosed for carrying out the method which consists of aheated spray chamber and an atomizer for spraying a solution of solventand sample into the chamber and a condensing chamber in fluidcommunication with the heated spray chamber. The condenser is connectedto a suitable burner, preferably a laminar flow burner.

A burner head, particularly adapted for use with fuel-s of high burningvelocity is also disclosed, which generally comprises a head member withan elongated slot therein and removable strips and spacers such that aplurality of narrow slits, the width of which may be varied, areprovided.

This invention relates to a burner system for spectroscopic analysisand, in particular, to a burner system which is most advantageously usedfor atomic absorption analysis.

Generally in spectroscopic analysis the sample is fed into the flame ofa burner in the form of a fine mist. If the mist is generated in aconventional atomizer burner by aspirating the sample with one of theflame gases at the bottom of the flame, a large gas stream velocity isrequired. Therefore, only fuel gases with high burning velocities suchas acetylene or hydrogen can be used with the conventional atomizerburner. Also, because of its shape, the flame of the atomizer burnerprovides only a short absorption path for the crossing light beam of amonochromator. Furthermore, increasing the sample spray rate and hencethe atom population of the analyte (the substance being analyzed) in theflame to enhance analytic sensitivity causes a sharp drop in flametemperature and the flame becomes more noisy and less transparent due toincomplete evaporation of the sample. Yet, for some elements the highflame temperatures which can be obtained with the combustion gases usedin the atomizer burners are mandatory.

Therefore, the burners more widely used in atomic absorption analysisutilize combustion gas mixtures with relatively small burning velocitiesand flame temperatures, such as coal gas, propane, or acetylene-airmixtures. These flames are acoustically quiet, have a laminar gas flowpattern and can be maintained in a lengthy, extended form, thus forminga long absorption path for the light beam. Hereinafter, such burnerswill be referred to as laminar flow burners. However, unlike theatomizer burner, direct atomization of a sample is not feasible for theslow burning flame of a laminar flow burner. Therefore, separate spraychambers have been used in the past in connection with the burner. Thesample is atomized and sprayed into the spray chamber and is premixedwith the combustion gases for the burner and then delivered into theburner. This in an inefiicient method since a large percentage of thesample globules generated by the atomizer hits the walls of the spraychamber and the larger drops settle out on the way to the burner-head.Moreover, the gas stream can only carry a moderate mist concentration.Deliberate overloading of the gas stream with mist causes only a highrecombination rate of smaller sample globules to larger drops. Hence,the sample loss to the walls of the spray chamber increases rapidly withthe overload of sample and makes the method more and more inefficient.Also, the flame itself can only evaporate a certain amount of samplecompletely. If it is overloaded with mist, it can cool down so far thatthe chemical compounds of the sample are no longer broken downefiiciently. Beyond a certain limit, the flame will die out or becomeintolerably nontransparent due to light scattering at the non-evaporatedwater drops.

It is, therefore, the principal object of the present invention toovercome the above disadvantages by providiug a burner system whichincreases the sample vapor in the flame of a burner without overloadingthe flame with solvent mist or vapor.

It is a further object of the invention to provide a burner system foratomic absorption or the like which provides uniformity and fineness ofsample fed to the flame and much higher sensitivity and stability overconventional burners.

A further object of the invention is to provide a burner for atomicabsorption analysis which eliminates flashback, provides a stable, wideflame and is highly versatile.

According to the principal aspect of the present invention, a largeconcentration of atomic vapor greater than that heretofore obtainable ismade available in a flame for spectroscopic analysis. The sampledissolved in a solvent is first atomized and sprayed into a heated spraychamber. The solvent in the spray is evaporated in the spray chamber totransform the sample mist into the form of an aerosol, which isunderstood to mean a cloud of small solid particles of clustered analytemolecules. Thereafter, the vaporized solvent and sample aerosol aredelivered to a condensing chamber in which most of the solvent iscondensed on the walls of the chamber thereby leaving only a fraction ofthe solvent and the aerosol in the chamber which is delivered to aburner to be mixed with the flame-gases of the burner. By this method, ahigh concentration of sample in the flame of a burner is providedwithout overloading the flame with solvent mist or vapor and, therefore,the sensitivity of the burner is greatly increased.

According to a secondary aspect of the present invention, there isprovided a burner which is particularly advantageous for atomicabsorption analysis. The burner has a chamber therein which converges toa narrow elongated slot at the upper end of the burner. Rather thanhaving merely a single slot at the outlet end of the burner, there isprovided an elongated strip positioned lengthwise in the slot to dividethe slot into two narrow slits. This arrangement permits a wider flameto be delivered from the burner and prevents flashback in the burner. Afurther feature of the improved burner is a means for changing the widthof the slits at the tip of the burner so that different types of gasesmay be used in the burner.

Other objects, aspects and advantages will become apparent from thefollowing description taken in connection with the accompanying drawingswherein:

FIG. 1 is a partial longitudinal sectional view through the burnersystem of the present invention;

FIG. 2 is a perspective view of the burner of the present invention withthe shield around the burner partly broken away;

FIG. 3 is a longitudinal sectional view through the novel burner of theinvention;

FIG. 4 is a fragmentary view of the shoulder plate on the top of thebody of the burner; and

FIG. 5 is a partial longitudinal section through a modified form of theburner system of the present invention.

Referring now to the drawings in detail, the principal components of thenovel invention are a housing 10, an atomizer sprayer 12, heating means14, a chamber 15, a condenser 16 and a burner 18. In accordance with themethod of the invention, a sample is first dissolved in a suitablesolvent and is atomized and sprayed through the sprayer 12 into thechamber 15 preferably by means of the oxidant which is used in theburner 18. The sample spray or mist is heated in chamber 15 tocompletely evaporate the solvent and to transform the sample into anaerosol. Then the oxidant-evaporated solvent-aerosol mixture passes fromthe chamber 15 into the condenser 16 where the major portion of theevaporated solvent vapor condenses on the walls of the condenser and theremainder of the solvent (approximately becomes again the form of a mistwhich is microscopicaly fine and very uniform. The formation of a mistwill mainly occur around the sample particles of the aerosol. A smallpercentage of the sample particles hitting the walls of the condenserwill be lost for the analysis. However, a much greater percentage of thesolvent vapor than of the aerosol is condensed out from the mixtureentering the condenser. Therefore, as to the gases which are deliveredto the burner and maintained in the flame, the ratio between the solventand the sample is increased many-fold over that obtainable byconventional burner systems which results in significant improvements insensitivity.

Although any suitable design of the various parts described above may beutilized, two preferred embodiments of the invention are disclosedherein for purposes of illustration.

Referring now to FIG. 1 in detail, the chamber is preferably cylindricalin shape and is concentrically positioned with respect to thecylindrical condenser 16. Both the chamber and condenser 15 and 16 aredisposed at an angle with respect to a horizontal plane for the reasonas will appear later. At the upper end of the housing 10 there isprovided a central opening 20 which receives a circular plate 22 whichcloses the opening. The plate 22 has a central opening 24 in which thereis mounted the tip of the sprayer 12 fixed to the housing 10 by bracket13. A duct 27 connects the inlet of the sprayer to a pressurized sourceof oxidant (not shown) used for the burner which may be either oxygen orair, and duct 26 delivers a sample disolved in a suitable solvent to thesprayer. It is important that the sprayer 12 has high stability sincethe stability of the whole burner system depends greatly upon thesprayer. Any drift in the spray rate will show up in a change in thesignal of the spectrophotometer (not shown) used in connection with thissystem. The sprayer must, therefore, be of high quality. It has beenfound to be advantageous to provide a plurality of openings 28 in theplate 22 which surround the sprayer tip 12 so that some air is suckedinto the chamber 15 under general operating conditions. The passage ofair through the openings 28 tends to smooth out the pressurefluctuations, if any, of the burner especially at the onset of the feedof the sample-solvent mixture into the chamber. Without these openings,it is possible that the flame may be blown out when spraying is started.

Once the sample spray or mist is in the chamber, the chamber must beheated sufliciently to completely evaporate the solvent in the spray. Aconduction type heating chamber may be used, as has been usedoccasionally in the art, however, such a chamber has the disadvantagethat the cooling of the walls causes drifting, especially at continuedhigh spray rates of sample into the chamber. Thus, in accordance withthe present invention, it has been found most advantageous to overcomethe problem of drifting by utilizing infrared heating to evaporate thesolvent which is sprayed into the chamber 15. Infrared heating has theadvantage that the fine sample drops evaporate before they have theopportunity to hit the walls of the chamber and thus are lost foranalysis. The infrared heating chamber 15 is shown in FIG. 1 as boundedor defined by a central cylindrical wall 30 of near infraredtransmitting, glass, the plate 22, and a portion of the end plate 64.Fused silica or preferably Pyrex may be used for the glass cylindricalwall 30. The cylindrical glass wall 30' is positioned within a centralopening 32 in a boss 33 in the end plate 34 of the condenser 16 and theupper end of the glass wall bears upon an annular shoulder 36 on the cap22. A pair of annular plates 38 and 40 surround the glass Wall 30 and acylindrical reflector 42 is connected by any suitable means to the twoplates 38 and 40*. A heating wire 44 is wound in the annular spacebetween the reflector 42 and cylindrical glass wall 30 and has a pair ofleads 46, only one being shown, which extends outside the housing 10 forconnection to a suitable power source. Preferably, the heating wire 44consists of NiCr which is wound in the form of a small, long spiral andconnected in a zig-zag manner to the opposite plates 38 and 40 by hooks47. The use of the infrared heating system is important because the heattransfer does not only occur along the heated wall, but within the totalvolume of the chamber. Furthermore, because the temperature of theheater 14 is appreciably higher than the temperature which would befeasible for a chamber with walls heated by thermal conduction, thespectral energy distribution of the radiation in the novel chamber ismore favorable for the evaporation of the solvent in the spray than thatobtainable in a conduction heated chamber.

As mentioned before, heated spray chambers are old in the art for usewith burners for spectroscopy. However, the problem with theconventional spray chamber and burner combination is that the flame ofthe burner can handle only a certain amount of water vapor or solvent. Alarge amount of vapor in the hot combustion gases of the burnerincreases the streaming velocity at the burner tip markedly while at thesame time diluting the combustion gases and reducing the burningvelocity. Therefore, the flame is lifted off from the burner tip andextinguished. Thus, the problem which must be solved is to remove mostof the water vapor from the gas stream while retaining the sampleaerosol in the burner gases. This is performed in the present inventionby means of a condenser 16. The condenser may have any suitableconfiguration and is shown in FIG. 1 as comprising a cylindrical housing48 which is attached to the housing 10 by welding 50 or the like at thejoint of the two housings. A cooling coil 52 in the form of a hollowtube is wound about the housing 48 of the condenser and also extendsaround the housing 10 to reduce undesired outside radiation from theheater. The coil 52 is connected to any suitable supply of water orcooling liquid, not shown. Within the cylindrical housing 48, there ispositioned a second cylindrical member 54 which has a plurality of ringshaped cooling plates 56 connected thereto. Positioned within thecylinder 54 is a second cylinder 58 also having a plurality of ringshaped cooling plates 60 positioned between the plates 56 therebyproviding a bellow-shaped path for fluid flow through the condenser. Endplates 62 and 64 are positioned at the opposite ends of the cylinder 54and each is provided with openings 66 and 68, respectively, forpermitting the flow of gas therethrough. An end plate 70 closes the openend 72 of the condenser 16 and is integral with the end of the cylinder58. The end plate has an opening 7-3 therein for receiving a centralduct 76 and an opening 78 which permit the flow of cooling liquidthrough the central cylinder 58. Thus, there is provided by thiscondenser an arrangement whereby the gases passing from the spraychamber 15 have a long path to slide along the cool surfaces of thecondenser to remove the solvent from the gas.

Due to the difference in the diffusion rate between the Water moleculesin the gas phase and the particles of the aerosol, which can beconsidered as huge molecules, the concentration of water vapor decreasesmore than the concentration of the analyte particles while thevapor-aerosol mixture is sliding along the cooled walls of thecondenser. It should be noted that the spacing between the coolingplates 56 and 60 should be large enough to avoid a partial obstructionof the gas path by drops formed from condensed solvent,

A small outlet 80 is provided at the lower end of the condenser 16 sothat condensed solvent may run down the inclined condenser and drain outthrough the opening 80. From there, the liquid may be drained to waste.

After the major portion of the solvent is condensed in the condensingchamber 16, the sample aerosol and a very small portion of the remainingsolvent passes through the openings 66 in the end plate 62 and pass outan outlet 74 at the end of the condenser. The outlet 74 has an opening75 which receives a fuel line 77 for delivering fuel to the burner 18.The outlet duct 74 is connected by a sleeve 81 to the burner inlet 82.The duct 74 and inlet 82 must be of suflicient length to permit acomplete mixing of the aerosol-oxidant mixture and the fuel from thefuel line 77 before reaching the burner 18. The burner is shown assurrounded by a chimney 84 having a window 86 therein through which thelight beam of a monochromator (not shown) extends.

The preferred burner to be used with the chamber 15 and condenser 16 ofthe invention is shown in detail in FIGS. 2 to 4. The burner includes abody portion 88 which is somewhat wider than the inlet 82 and is taperedtowards its upper end as seen in FIG. 3 and is provided with a chamber90 which converges towards the upper portion of the burner. A shoulderplate 92 having an elongated narrow slot 94 is integral with the upperportion of the body 88 of the burner and the slot 94 is aligned with thechamber 90. The shoulder plate may be cooled by means of a cooling coil,not shown, which surrounds the body of the burner 88 just below theshoulder plate, The body 88 includes a novel burner head 96 which isseated on the upper flat surface of the shoulder plate 92.

The burner head consists of two symmetric-a1 pieces 98 and 100 whichhave recessed, flat, parallel walls 102 and 104 and tapered outer walls103 and 105. When the two pieces 98 and 100 of the head are fastenedtogether by screws 6 and 108, a narrow slot 110 is provided between thewalls 102 and 104 which is aligned with the slot 94 in the shoulderplate 92. While the main portion of the burner may be made of aluminum,it is preferable that the head be made out of stainless steel to reduceunwanted changes in the dimensions of the slot 110 during operation.Positioned between the two pieces of the head 98 and 100 is an elongatedmetal strip 111, preferably of stainless steel, which is the same heightas the head 96 and extends for the full length thereof thereby dividingthe slot 110 into a pair of narrow slits 112 and 114. The head 96 isafiixed to the shoulder plate 92 of the burner by means of suitablespring clips 116 and 118 so that the head may be readily removed fromthe burner. An important feature of this burner head is that it may beremoved from the burner body and the screws 106 and 108 removed so thatmetal strips 111 of different thickness may be disposed between the twopieces 98 and of the burner head and, also, spacers 117 and 119 may bepositioned on either side and at both ends of the strip 111. By addingthese spacers or additional spacers and changing the thickness of thestrip 111, both the over-all width of the slot 110 and the width of theslits 112 and 114 of the head may be increased as desired which makesthe burner extremely versatile for use with different types of fuel. Ifthe slot of the burner head has a fixed dimension, only one fuel may beused with a given combustion gas volue. By increasing the thickness ofthe strip 111 the width of the flame produced by the burner is increasedwhich permits a wide optical beam to be used and thus a greaterphotometric sensitivity and a better signal to noise ratio is achieved.Preferably, the metal strip 111 is tightly clamped at one end betweenthe side pieces 98 and 100 and the other end is kept loose enough toallow independent thermal expansion. Hence, thermal tensions areprevented from being generated between the burner head and the rest ofthe burner and, thereby, slot distortions which occasionally occur inone piece burner assemblies are prevented. The strip 111 serves theadditional important function of preventing flash-back into the burnerWhile still permitting a relatively wide double slot 110 for the flame.Without the elongated strip, the over-all width of the slot 110 wouldhave to be about the same size as the width of either of the slits 112or 114 to prevent flash-back.

A further important feature of the burner is the provision of thechimney 84 which is fitted on the burner by sliding the chimney over theburner with the slots in the chimney registering with the tabs 122 onthe sides of the body of the burner. The chimney not only provides ameans for protecting the flame from side drafts and thus providesstabilization of the flame, but also adds to the shaping of the flamecross-section. Whether the flame is wide or narrow depends upon thestream of air at the burner head. The flame stability may be optimizedif the air stream which supplies a portion of the oxygen for combustionof the fuel is fed to the flame from below, at a slight angle. The airflow should be smooth and steady. This is achieved by having the chimneyextend far below the burner head and having it spaced from the walls ofthe burner so that cold air is sucked in from underneath the burner andslides up in laminar flow between the flat burner walls and the chimneythus cooling both the burner and the chimney. As best seen in FIG. 3,the sides of the shoulder plate 92 of the burner are close to thechimney, thereby providing a restriction for the air stream. Due to thisrestriction and the streamlined profile of the burner head 96 providedby the tapered walls 103 and 105, the air slides along the tapered wallsof the tapered burner head 96 and strikes the flame under a slight anglefrom underneath. The delivery of air to the flame in this manner greatlyenhances the stability of the flame. By the novel head of this burnerand the chimney surrounding the burner, a burner is provided which hasgreatly improved stability, versatility, is free from flash-backs, andmay have an adjustable burner slot to accommodate different fuels.

The table below shows the concentration of several samples in ppm. whichprovides one percent absorption when a light beam from a monochromatorpasses through a flame containing the sam le.

Sample concentration (p.p.m.) which provides 1% absorption Theconcentrations listed in column A were determined by using a burner asshown in FIGS. 24 which received the samples from a spray chamber andcondenser apparatus as shown in FIG. 1. In column B, the sample concentration for each sample listed is obtained from data appearing inPerformance of a Simple Atomic Absorption Spectrophotometer by B. M.Gatehouse and I. B. Willis in Spectrochemia Acta, 1961, vol. 17, pp.710-718, in which a conventional laminar flow burner system was used. Bycomparing the concentrations listed in columns A and B it can be readilyseen that the system of the present invention required much lessconcentration of sample for the same amount of absorption of the lightbeam than required in the conventional system. In other words, thesystem described herein has much greater sensitivity than theconventional system. It is to be noted that the sensitivity of theburner system of this invention would be the same as listed in the tableabove even if a conventional burner were used rather than that shown inFIGS. 24 because the burner provides stability in the flame andversatility but not sensitivity.

In FIG. 5 there is shown a slightly modified form of the burner systemof the present invention. The heating chamber and sprayer 12 are thesame as is shown in FIG. 1 whereas the condenser 16 differs only incertain details as will be described below. The important feature ofthis embodiment of the invention is that a low profile burner 124 isprovided so that a conventional monochromator may be used with theburner system that need not be mounted in a high position so that thelight beam will coincide with the window in the chimney 84 surroundingthe burner. The low profile is provided by removing the inlet duct 82 ofthe burner and replacing it with a duct 126 which extends centrally intothe condenser 16, in which duct the mixing of oxidant, fuel and sampletakes place prior to the delivery thereof to the burner. The body 88 andhead 96 of the burner 124 are essentially the same as that shown inFIGS. 2 to 4 and the burner is preferably surrounded by a chimney, notshown.

The condenser in FIG. 5 comprises an outer cylinder 127 in which thereis mounted a pair of perforated end plates 128 and 130. These plates areconnected to an inner cylinder 132 which surrounds the tube 126. Coolingducts 134 surround the cylinder 127 and additional cooling ducts 136surround the cylinder 132. Hence, vapor and aerosol from the chamber 10passing through the perforated plate 128 flow along the cool surfacesbetween the walls of the outer cylinder 127 and the inner cylinder 132,through the perforated plate 130 at the other end, and back toward thefirst end plate 128 to the inlet end 140 of the duct 126. A second tube138 has at one end an opening into the inlet end 140 of the tube 126 andhas its other end extending outwardly from the condenser for connectionto the fuel source, not shown, for the burner 12 4. Thus, after themajority of the solvent in the spray is condensed in the condenser 16,the aerosol will mix with the burner fuel in the duct 126 and completemixture thereof will be obtained by the turbulent flow through the ductby the time the mixture reaches the outlet end 142 of the duct 126. Itcan be readily seen therefore that a compact, low profile burner systemis provided by this arrangement which does not require any specialmounting of a monochromator used therewith.

It is to be understood that the burner system of the present inventionmay be used for other types of spectroscopic analysis other than atomicabsorption. For example, the heating chamber 15, sprayer 12 andcondenser 16 combination may be used for flame emission spectroscopywith only slight modification, and a conventional type of laminar flowburner may be used other than the burner shown in FIGS. 2 and 4 in thedrawings. Even an atomizer burner could be used. In such a case, thespray chamber would have to be made air tight to permit the build up ofnecessary pressure to deliver the aerosoloxidant mixture to the burner.The burner system can also be used when the spray chamber is not heated.In this case sensitivities similar to that of a conventional burnersystem are obtained. This means that the analytical range can be changedeasily when high sensitivities are not required, yet all the favorablestability features of the system are maintained.

Although several embodiments of the invention have been disclosed hereinfor purposes of illustration, it will be understood that various changescan be made in the form, details, arrangement and proportions of thevarious parts in such embodiments without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:

1. In a method for providing a large concentration of atomic vapor in aburner flame for spectroscopic analysis, the steps comprising:

providing a solution comprising a sample dissolved in a solvent;

transforming said solution into a spray;

heating said spray to evaporate said solvent and to transform the sampleinto an aerosol;

condensing the evaporated solvent; and

delivering the aerosol to a burner for spectroscopic analysis.

2. In a method for providing a large concentration of atomic vapor in aburner flame for spectroscopic analysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

transforming said solution into a spray;

heating said spray to a sufficient temperature to evaporate said solventand to transform the sample into an aerosol;

condensing the evaporated solvent; and delivering the aerosol to aburner for spectroscopic analysis.

3. A method as set forth in claim 2 wherein the heating of said spray isperformed with infrared energy.

4. A method as set forth in claim 2 wherein said spray is heated to asufficient temperature to completely evaporate said solvent.

5. A method as set forth in claim 2 wherein said solution is transformedinto a spray by a pressurized burner oxidant.

6. In a method for providing a large concentration of atomic vapor in aburner flame for spectroscopic analysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

spraying said solution by a pressurized burner oxidant into a chamber;

heating the sprayed solution in said chamber to evaporate said solventand to transform the sample into an aerosol; delivering the evaporatedsolvent and aerosol to a condenser;

heating said spray to a sufficient temperature to coinpletely evaporatesaid solvent and to transform the sample into an aerosol; and

condensing the major portion of the evaporated solvent on a surfaceother than the aerosol whereby a large concentration of sample aerosolis provided.

8. In a method for providing a large concentration of atomic vapor in aburner flame for atomic absorption or flame emission spectroscopicanalysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

spraying said solution by a pressurized burner oxidant into a chamber;

heating the sprayed solution by infrared energy to a suflicienttemperature to completely evaporate said solvent and to transform thesample into an aerosol;

delivering the evaporated solvent and aerosol to a condenser;

condensing the major portion of the evaporated solvent onto the Walls ofsaid condenser;

mixing the aerosol, the remainder of said evaporated solvent and burneroxidant with a burner fuel; and burning said mixture in a burner forspectroscopic analysis.

9. In an apparatus for providing a large concentration of sample aerosolfor delivery to a burner for spectroscopic analysis, the combination of:

a chamber;

means opening into said chamber for spraying a solution of sampledissolved in a solvent into said chamber;

means for heating the spray to suflicient temperature to evaporate thesolvent into a vapor and to transform the sample into an aerosol;

vapor condensing means in fluid communication with said chamber forcondensing the major portion of .the vapor onto the walls of thecondensing means;

and

said vapor condensing means having an outlet for connection to a burner.10. An apparatus as set forth in claim 9 wherein said heating meansproduces infrared energy.

11. An apparatus as set forth in claim 9 wherein said outlet comprises atube having an inner end extending into said condensing means and saidcondensing means including a duct having one end opening into said innerend of said tube and the other end extending outside of said condensingmeans for connection to a burner fuel supply.

12. An apparatus as set forth in claim 9 wherein said chamber includes aWall of infrared transmitting material and said heating means comprisesa reflector positioned adjacent said wall and a heating wire positionedbetween said reflector and said wall of transmitting material.

13. In an apparatus for providing a large concentration of sampleaerosol for delivery to a burner for spectroscopic analysis, thecombination of: a chamber having a Wall portion; means in said wallportion for spraying a solution of sample dissolved in a solvent intosaid chamber;

said wall portion having a plurality of openings surrounding saidspraying means to compensate for pressure fluctuations caused by saidspraying means;

means extending about said chamber for generating infrared energy ofsufficient amount to evaporate the solvent into a vapor and to transformthe sample into an aerosol;

vapor condensing means in fluid communication with said chamber, saidvapor condensing means for condensing the major portion of the vaporonto said vapor condensing means; and

said vapor condensing means having an outlet for connection to a burner.

14. In a burner system for spectroscopic analysis, the combination of:

a chamber;

means for spraying a solution into said chamber;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber; and

a burner having an inlet connected to said condensing means.

15. A burner system as set forth in claim 14 wherein said heating meansproduces infrared energy.

16. A burner system as set forth in claim 14 wherein said burner issubstantially vertically disposed and said condensing means has anopening at the lower end thereof adjacent to said burner and saidcondensing means is tilted at an angle with respect to a horizontalplane whereby condensed vapor may escape from said condensing means.

17. In a burner system for spectroscopic analysis, the combination of:

a chamber having a wall portion;

means in said wall portion for sprayinga solution into said chamber;

said wall portion having a plurality of openings surrounding saidspraying means;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber; and

a burner having an inlet connected to said condensing means.

18. In a burner system for spectroscopic analysis, the

combination of:

a chamber;

means for spraying a solution of sample dissolved in solvent into saidchamber;

heating means for evaporating said solvent into a vapor and fortransforming the sample into an aerosol;

vapor condensing means in fluid communication with said chamber, saidcondensing means having an outlet tube with one end extending into saidcondensing means and the other end outside said condensing means;

a duct having one end opening into said one end of said outlet tube andthe other end extending outside of said condensing means for connectionto a burner fuel supply whereby the aerosol and fuel are mixed in saidtube; and

a burner connected to said outlet tube.

19. A burner system as set forth in claim 18 wherein said burner issubstantially vertically disposed and said condensing means has anopening at the lower end thereof adjacent to said burner and saidcondensing means is tilted at an angle with respect to a horizontalplane whereby condensed vapor may escape from said condensing means; and

the upper end of said burner being below the upper end of said chamberand condensing means.

20. In a burner system for spectroscopic analysis, the

combination of:

a chamber;

means for spraying a solution into said chamber;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber;

a burner having an inlet connected to said condensing means, said burnerincluding an inlet for a burner fuel;

said burner having a body with a chamber therein converging to a narrowelongated slot at the upper end of said body and an elongated strippositioned lengthwise in said slot dividing said slot into two narrowslits.

21. In a burner system as set forth in claim 20 including means forvarying the width of said slot.

22. In a burner system for spectroscopic analysis, the combination of:

a chamber;

means for spraying a solution into said chamber;

1 1 l 2 heating means for heating said chamber; 3,163,699 12/1964Staunton 88--14 vapor condensing means in fluid communication with1,330,464 11/ 1931 l nt r.

Said chamber; 8 OTHER REFERENCES a burner having an inlet connected tosaid condensing Meloche. Flame Photometry Analytical Chemistry means;said burner lncluding an inlet for a burner 5 VOL 28, NO 12 December1956 p 1845 relied On- .fuel; Menzies: A Study of Atomic AbsorptionSpectrosaid burner terminating in a burner head having a scopyAnalytical Chemistry, VOL 32 8, July 1960) plurality of slits therein.

References Cited 10 JEWELL H. PEDERSEN, Primary Examiner. UNITED STATESPATENTS F. L. EVANS, Assistant Examiizen 2,828,532 4/1958 Taylor 158116X 2,857,801 10/1958 Murray 158111 X 2,959,217 11/1960 Barnes et a1239-652 239552, 568, 590, 597; 356-87, 187

